TV has already been a part of people's lives. Along with development in digital communication, functions provided by TV are expected to attain greater sophistication. For instance, digital TV broadcast for portable equipment such as a portable telephone will be introduced in the near future, using a segment of satellite broadcast.
As for the reasons of such popularity of TVs, besides the contents of broadcast, easy operation of TVs should not be ignored. Particularly, broadcast channels are allocated to prescribed frequencies beforehand, and a so-called channel selector for selecting a broadcast channel is provided on the TV. The oldest form of channel selector was a knob-type one that can rotate 30 degrees at a time about the central axis. Turning of the knob allows selection of any one among 12 channels. This operation was so intuitive and very easy to understand that anyone can operate the TV.
Recently, however, not only radio broadcast but also cable broadcast are often viewed by one TV receiver. This means too many channels to be selected by the knob-type selector described above. While a remote controller (a so-called “remote”) has been widely used to operate TV from a distance, it is difficult because of space limitations to provide a knob-type channel selector on the remote. This leads to provision of numerical keys on the remote, and the user generally designates a channel using the numerical key.
Still, similarly to the operation of old, knob-type channel selector, when a user switches from one channel to another, the general operation is to move to the “neighboring” channel. Keys for this purpose (up/down keys) are provided on the remote. When one presses the up-key, the channel is switched to an upper one, and when one presses the down-key, the channel is switched to a lower one. The channel returns to the first one after one round. This is similar to the operation of the old, knob-type channel selector, and anyone can easily do this operation.
Patent Document 1: Japanese Patent Laying-Open No. 2002-44536